Background: Few data are available on the association between birthweight, birth order (BO), and age at menarche. Previous studies have indicated a significant association between birthweight, BO, and age at menarche. Aim: this cross-sectional study examines the association between birthweight, BO, and age at menarche of Nigerien schoolgirls. Materials and Methods: Sociodemographic and anthropometric data were collected with questionnaires from a total of 487 adolescent schoolgirls aged 12–27 years. Results: Schoolgirls with low birthweight reach menarche earlier than those with normal birthweight (13.59 years vs. 13.94 years, P= 0.004). BO showed statistically significant impact on age at menarche with the first-born girls reaching menarche earlier than the later-born girls (F = 5.17,P Conclusion: Our results suggest an association between birthweight, BO, and age at menarche.